Azaleas are a small flowering shrub which is a member of the rhododendron family. Originally azaleas were classed as a different family of plant, but now they are recognised as two of the eight sub-genera of rhododendrons - Subgenus Pentanthera typified by Rhododendron nudiflorum and Subgenus Tsutsusi typified by Rhododendron Tsutsusi.
One of the major differences between azaleas and the rest of the rhododendron family is their size. Another is their flower growth. Rhododendrons grow their flowers in clusters, while most azaleas have terminal blooms (one flower per flower stem). However, they have so many stems that during the flowering season they are a solid mass of colour. The exception to this rule is a small group of azaleas which grow their flowers in tight terminal clusters that look like little balls of colour.